1. FIELD OF THE INVENTION
This invention relates to pre-cast traffic barriers for use in highway construction More specifically, the present invention relates to a pre-cast concrete traffic barrier and a method of constructing a traffic barrier on the top face of a retaining wall or other supportive horizontal beam.
Traffic barriers are used on roads to keep a moving vehicle from crossing into the path of oncoming traffic or from driving off the roadway. The traffic barrier is especially useful on elevated or split-level roadways, such as bridges, entrance ramps, or access roads to highways, to prevent a vehicle from driving off the road onto a lower level roadway. These elevated roads are often formed by cutting through a hill or by piling earth or soil onto metal reinforcements to form a laterally stabilized composite earth structure to support the road. Either method of construction may result in a wall face which needs to be supported by a retaining wall. If this retaining wall is close to the road surface there is a need for a traffic barrier which can be anchored on top of the retaining wall. The wall, of any height, defines a lengthwise horizontal beam for anchoring the barrier.
Construction of a traffic barrier on top of and along a retaining wall may be cast-in-place so as to be an integral part of the retaining wall. However, this construction method requires forms to be constructed by workmen on scaffolding. Hand construction of the forms and pouring of concrete is slow and labor intensive Thus, there is a need for a more efficient method of constructing a traffic barrier onto the top face of a retaining wall.
2. DESCRIPTION OF THE PRIOR ART
Basic traffic barriers separating two lines of vehicular traffic are not new in the art. U.S. Pat. No. 3,678,815 issued to Younker discloses a concrete traffic barrier which may be used in forming bridge guard rails, median barriers, and the like. The Younker barrier includes a pair of identically shaped shells which are bolted together leaving a void into which concrete is poured to form a core of solid material. U.S. Pat. No. 4,435,106 issued to Forster et al. discloses a traffic barrier which may be used to separate a roadway. The Forster traffic barrier may be cast-in-place through the use of forms to construct a solid concrete barrier which rises from the roadway edge outwardly first gently and then more strongly and then spaced below an overhanging guiding mechanism. A steep convex rise follows the gentle rise and transfers under the guiding mechanism into a flattened area.
Combining steel and concrete in a traffic barrier was disclosed in U.S. Pat. No. 4,496,264 issued to Casey. Casey discloses a barrier structure comprised of a number of spaced apart inline vertical I-beam sections embedded in a roadway and having secured to the I-beams a number of form plates having a pair of downwardly and outwardly diverging pair of legs and a pair of upwardly diverging extending arms. Reinforcing rods are extended through aligned holes in the plates and side panels are connected to the panels. Concrete is poured down through the open top of the structure completely encasing the I-beams, panels, and reinforcing rods. The concrete bonds the side panels and a capping piece is pressed down into the concrete to form the steel and concrete traffic barrier.
Constructing concrete traffic barriers with pre-cast concrete was first patented by Smith in U.S. Pat. No. 4,059,362. Smith discloses a highway traffic barrier composed of pre-cast, reinforced concrete barricades which are joined together. The alignment with each barricade is accomplished through the use of a horizontally and vertically tapered, vertical tongue-and-groove arrangement. This tongue-in-groove arrangement is molded onto the ends of each barricade with the wider portion of the taper at the bottom to facilitate the removal of one piece of the traffic barrier within an installation. The Smith barricade though is designed to be a highway median barrier and cannot be secured to a retaining wall.
A pre-cast barrier design which can be used on retaining walls is disclosed in U.S. Pat. No. 4,494,892 issued to Wojciechowski This design makes use of an interior channel of the barrier which directly contacts the top edge of the retaining wall. The projecting anchoring rods extend either transversely into a lateral pre-cast concrete apron under the roadway surface or downwardly into the earthen support of the roadway. These projecting anchoring rods provide external support of the traffic barrier which is lacking in the original barrier element. The anchoring rods provide the support to withstand impacts from moving vehicles.
Another known pre-cast traffic barrier is U.S. Pat. No. 4,348,133 issued to Trent disclosing a pre-cast polymer concrete shell which is placed at the construction site then filled with hydraulic concrete or other ballast through filling holes on top of the shell. However, the shell cannot be placed on a retaining wall since the shell must be entirely placed on the road or bridge surface.
A method of joining pre-cast concrete barriers on substantially flat roadway surfaces is disclosed in U.S. Pat. No. 4,605,336 issued to Slaw. This design uses an upwardly projecting inverted U-shaped rod, which must be inserted into a narrow longitudinal channel, and a concrete reinforcing rod extending axially through the channel forms a longitudinal locking bar inserted to lock the barrier to the retaining wall. One problem with this design is that it can only be used on a substantially flat roadway and the alignment of the pre-cast barrier and roadway must be precise to insure that the U-shaped rods are inserted into the rectangular inserts. Another limitation is a lack of tongue and groove connection to secure the barrier in place.